The technical field of this invention is electro-stimulation of tissue in vivo for therapeutic purposes.
The use of acupuncture to relieve pain and produce other therapeutic results has been common in certain cultures for many years, but only recently has this practice gained a significant following in the United States. The increased recognition of the utility of acupuncture in medicine has led to new forms of acupuncture therapy such as electro-acupuncture, in which the acupuncture needle is connected to a power source to deliver an electric current to an acupuncture point. Electro-acupuncture has the potential to combine the benefits of conventional acupuncture with the advantages of electrical nerve stimulation.
Such new acupuncture practices require the development of devices and methods suitable for safe, reliable delivery of an electric current via an implantable needle. Implantable electro-acupuncture devices have been described (e.g., U.S. Pat. Nos. 5,094,242 and 5,211,175 to Gleason et al.). However, although these devices solve many of the problems associated with prior art devices for electrical stimulation, they may not be suitable for long-term implantation due to the possibility that their needles will move or shift within tissue, thereby removing the needles from the desired site of electrical stimulation over time. Moreover, the relatively inflexible needle of previous devices may not be able to accommodate a full range of tissue motion, with the accompanying risk of metal fatigue and eventual fracture of the needle or other device components, and possible damage to surrounding tissue. Furthermore, prior art devices often fail due to corrosion or short-circuits that occur as a result of the infiltration of body fluids into the device over time.
Improved implantable devices for electro-acupuncture and electrical stimulation having one or more flexible electrodes for delivering an electric impulse to tissue are herein disclosed. These devices may also include anchoring mechanisms for preventing motion of the conductor electrode relative to tissue, and/or may have sealed, liquid-tight housings. The implantable devices of the invention are suitable for implantation in a patient""s tissue for extended time periods.
In one aspect, the invention provides an implantable nerve stimulation device which includes a housing which defines a cavity, a source of electrical current disposed within the cavity, a first electrode for applying an electric current to tissue, and a second electrode in electrical connection with the source of electric current for receiving the electric current after the current has passed through tissue. The second electrode is in electrical communication with the source of electric current, and, preferably, is secured to the housing at a proximal end of the first electrode. The first electrode can be a flexible conductor, having a distal end adapted for conducting an electric impulse to the tissue.
In another aspect, the invention provides an implantable nerve stimulation device which includes a housing which defines a cavity, a source of electrical current disposed within the cavity, a first electrode for applying an electric current to tissue, and a second electrode in electrical connection with the source of electric current for receiving the electric current after the current has passed through tissue. The second electrode is in electrical communication with the source of electric current, has a distal end for applying an electrical current to tissue, and is secured to the housing at a proximal end of the first electrode. The first electrode further includes an anchor for fixing the distal end of the first electrode relative to the tissue and for resisting movement within the tissue.
In still another aspect, the invention relates to an implantable nerve stimulation device which includes a housing which defines a cavity, a source of electrical current disposed within the cavity, a first electrode for applying an electric current to tissue, and a second electrode in electrical connection with the source of electric current for receiving the electric current after the current has passed through tissue. The second electrode is in electrical communication with the source of electric current, and is secured to the housing at a proximal end of the first electrode. The housing is hermetically sealed to prevent ingress of body fluids into the cavity. The hermetically sealed housing may, for example, consist in part of a ceramic lid that allows high frequency energy to pass without being attenuated as with a comparable metal housing.
The implantable nerve stimulation device may also include a protective member, such as a strain relief boot, to protect the interface between the housing and the conductor, and/or may include a securing mechanism to suture a portion of the device to tissue in order to deter or prevent movement of the device from its site of implantation.
In any of the above aspects of the invention, an internal power source may act as the source of electrical current, wherein the internal power source can be activated and deactivated remotely.